In this study, new members of mono cationic basic ionic liquids were synthesized as water stable viscous liquid consisting of 1, 3‐dialkyl‐2‐methyl imidazolium cation and acetate (or hydroxide) anion. Their structures were determined using 1H NMR, 13C NMR, FT‐IR and elemental analysis. Thermogravimetric analysis displayed maximum stabilities of six ionic liquids up to 260 °C. The UV‐Vis technique was employed to determine their comparable Hammett basicity order. Thermally stable five ionic liquids with less moisture content showed their catalytic activities by formation of 85–97% yields of β‐amino carbonyl compound for the model Aza‐Michael reaction of piperidine and acrylonitrile in neat condition with 2 and 5 mol % of catalysts for 5–15 min at room temperature. The optimized two catalysts [dbIm]OH and [daIm]OAc were reused efficiently with slight loss of activity for four cycles after the 1st run.

Background: Four members of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates [DSTMG]n[X], where n= 1 or 2; X= FeCl4 - , Zn2Cl6 2-, NiCl4 2-, MnCl4 2- were synthesized as solid Brønsted-Lewis acidic compounds and studied the catalytic activity with the most acidic salt for three-component synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2- e][1,3]oxazin-3-ones. Methods: N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates of the four transition metal cations such as Fe(III), Zn(II), Ni(II) and Mn(II) were prepared after treatment of the parent ionic liquid N,N-disulfo-1,1,3,3- tetramethylguanidinium chloride [DSTMG][Cl] with the respective metal chlorides in different mole fractions at 75 ºC. The synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones was carried out via three-component reaction of 2-naphthol, aromatic aldehydes and urea under neat condition at 90 ºC using 7 mol% of the [DSTMG][FeCl4] catalyst. Results: The characterization of synthesized chlorometallates were done using spectroscopic and other analytical techniques including thermogravimetric analysis and Hammett acidity studies. Among the four salts, the salt of Fe(III) ion was observed as the strong Brønsted acidic hydrophobic salt and thus chosen for the catalytic study. Conclusion: A new type of chlorometallates of guanidinium cation with composition [DSTMG]n[X], where X= FeCl4 - /Zn2Cl6 2-/ NiCl4 2-/ MnCl4 2- and n= 1 or 2 were developed as –SO3H functionalized solid acids with varied thermal stability (150-250 ºC) and physisorbed water (0-20%) as observed from the thermogravimetric study. From them, the most Brønsted acidic Fe(III) salt was employed as efficient recyclable heterogeneous catalyst for the one-pot synthesis of 1,2- dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones in neat condition.

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Two series of basic triethylamine bridged pyridinium/imidazolium tricationic ionic liquids were synthesized as viscous liquids by ion‐pairing with hydroxide, acetate and imidazolide as basic anions. The characterization of tricationic ionic liquids was done using 1H and 13C NMR, FT‐IR, Thermogravimetric analysis (TGA), Hammett basicity EI‐MS and elemental analysis techniques. Thermal stabilities were found within the range of 100–150 °C for these ionic liquids. They acted as efficient recyclable homogeneous catalysts for the representative Knoevenagel condensation of benzaldehyde and malononitrile at room temperature stirring in neat condition for 10–20 min. The catalytic activity of these ILs was found to be slightly different from each other for the model reaction and did not follow the same sequence of their measured Hammett basicity value.

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